It is common practice in the installation of AM broadcast stations to put in an extensive ground system buried in the earth. In fact, the Federal Communications Commission (FCC) has mandated that each standard AM broadcast station be equipped with a ground system consisting of at least 120 radials, each being at least one-quarter wavelength in length. For the typical broadcast frequencies of 540 kHz to 1,700 kHz, this amounts to approximately 18,000 to 49,000 feet of wire which would occupy approximately 2 to 15 acres of clear land. The ground system for the typical AM broadcast antenna can be seen to be a very expensive and large undertaking.
The traveler's information AM broadcast stations, which are frequently seen at the entrances to airports, state parks, national parks and even at state borders, operate at a frequency in the range of approximately 530 kHz to 1,710 kHz, which is slightly below and slightly above the standard broadcast range of frequencies. The FCC has waived the above-mentioned ground system requirement for traveler's information stations; however, a practical station still requires a ground system in order for the antenna to radiate an effective signal. The small, low power, limited range transmitters employed in the traveler's information service cannot justify the expense of the typical antenna ground system. Even the amount of land occupied by a conventional ground system at the authorized frequencies would be prohibitive.
Known antenna ground systems may include a plurality of wires or other conductors that extend outwardly away from the antenna, generally parallel to the ground surface. Because of the large area required for the ground plane, the antenna cannot be positioned adjacent buildings or other structures. Furthermore, extensive labor may be required to install such ground planes.